Not like decay of β+ or EC(electron capture), in β- decay, the nucleus positive charges definitely exerts strong suck force to negative charged electron, and the heavier the nuclide, the stronger the force! So, no coulomb barrier for β+/EC, but does for β- decay. How can the electron in a β- radioactive isotope can overcome that super strong attractive force even in just a few energy Q(β-) of single digital KeV? Also wondering why no significant influence between light nuclides and heavy nuclides for the said factor. I guess it is the magic tunneling effect? And supposedly in β-, the initial velocity at the exit point should be smaller than the velocity at a little far distance to exit point, because the suck force is inversely proportional to the square of distance. But in fact, it seems not like that. Deducedly, in same energy Q(β), β+/EC should be easier than β-, that is why our universe is not symmetric in the abundance of quasi-stable isotope. For example, you can see the β- potential Rb-87 with abundance 28%, In-115 with abundance 96%, Re-187 with abundance 63% and Q(β-) only 2467eV, and so on, but nobody can enumerate high abundance of β+ potential nuclides. The God is really left-handed! There is electron capture, why is not there positive electron capture, or say positron capture decay? I boldly predict it should have e+ capture along with β- decay. Let's work hard to prove it.